It is believed that a chloroform-methanol soluble 8.5 K dalton lipoprotein located in the mitochondrial fraction of varied cell types is subunit 9 of mitochondrial ATPase complex. The apoprotein fraction of this proteolipid is a product of mitochondrial translation in varied mammalian cells. Recently, using double immunoprecipitation procedure we purified the mRNA coding for the apoprotein from total mitochondrial polysomes of Ehrlich ascites carcinoma cells. In this grant application it is proposed to undertake a detailed characterization of purified mRNA with respect to its physical, chemical and biological properties: 1) In vitro translation in prokaryotic, eukaryotic and mitochondrial ribosome systems, and characterization of the in vitro product with respect to N-terminal aminoacid sequence and fingerprint analysis. 2) Isolation of mRNA sequences 5' adjacent to the initiator codon and study their sequence property. 3) Characterization of biogenesis and mode of maturation of mitochondrial mRNA by extensive hybridization of mRNA and the cDNA with its putatire precursors and also with mitochondrial DNA.